WO2015146859A1 - ポリオレフィン微多孔膜およびポリオレフィン微多孔膜を用いてなるコーティング用基材 - Google Patents
ポリオレフィン微多孔膜およびポリオレフィン微多孔膜を用いてなるコーティング用基材 Download PDFInfo
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- WO2015146859A1 WO2015146859A1 PCT/JP2015/058607 JP2015058607W WO2015146859A1 WO 2015146859 A1 WO2015146859 A1 WO 2015146859A1 JP 2015058607 W JP2015058607 W JP 2015058607W WO 2015146859 A1 WO2015146859 A1 WO 2015146859A1
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- microporous membrane
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
Definitions
- the present invention relates to a polyolefin microporous membrane and a coating substrate using the same.
- microporous membranes are generally used in applications such as battery separators, capacitor films, and filters.
- various properties such as heat resistance, strength, and electrolyte retention are required.
- a method for realizing such required characteristics a method using a film obtained by coating a microporous film is becoming mainstream.
- Lithium ion batteries are expected to be used not only for small mobile devices such as mobile phones and laptop computers, but also for in-vehicle use in the future, and there is a need for improved productivity.
- MD direction machine direction
- the strength in the machine direction is strong, but if only the strength in the MD direction is increased too much, the anisotropy of the microporous film Since it is strong and easily tears during conveyance, it becomes difficult to control the tension during coating. Therefore, it is necessary to suitably adjust the intensity balance in the MD direction and the width direction (hereinafter referred to as the TD direction).
- Patent Document 1 a microporous membrane is manufactured by wet simultaneous different magnification stretching, and the strength balance in the MD direction and the TD direction (ratio of elastic modulus in the length direction and elastic modulus in the width direction) is adjusted. It is shown that a good slit property can be obtained. Furthermore, it is described that good withstand voltage characteristics can be obtained by adjusting the maximum pore diameter.
- Patent Document 2 a polyolefin, a plasticizer, and inorganic particles are mixed, and a microporous film is produced by successive stretching.
- the microporous membrane obtained by the above method has a uniform pore size, and achieves both good withstand voltage characteristics, permeability and strength.
- a heat-resistant porous layer is formed by coating one side or both sides of a base material (microporous film) and adjusting the density and viscosity of the coating material and the pore size of the base material. And a technique capable of preventing a decrease in ionic conductivity is described. However, a method for uniformly coating is not described.
- the stretching method and coating materials are adjusted to achieve good transportability, permeability, and withstand voltage characteristics to suppress deterioration of physical properties after coating, but coating unevenness during coating is also suppressed. It does not describe the technique to do.
- various types of coating materials have been adjusted and applied in order to perform uniform coating, but these are only from the viewpoint of the coating material, and are based on the requirements for uniform coating. The performance required on the material side is not clear. In order to perform high-speed conveyance and uniform coating, there is a limit only by adjusting the coating material and the coating method. Therefore, it is considered that a microporous membrane that can be applied uniformly from the viewpoint of the base material will be required in the future.
- JP 2010-007053 A International Publication No. 2005-061599 JP 2011-204587 A
- an object of the present invention is to provide a microporous membrane capable of uniform coating.
- the present invention is as follows. (1) When a plurality of measurement areas for measuring the pore size distribution are set apart from each other along the TD direction, the measurement results obtained in these measurement areas satisfy the following relational expression (A).
- (sigma) (Dexp) is the standard deviation calculated using Deexp calculated by the following formula
- Dexp ⁇ ⁇ Dj ⁇ (PSF) j ⁇ (Dj: hole diameter, (PSF) j: value of hole diameter distribution (frequency of hole diameter Dj) (2)
- Dexp ⁇ ⁇ Dj ⁇ (PSF) j ⁇ (Dj: hole diameter, (PSF) j: value of hole diameter distribution (frequency of hole diameter Dj)) (8)
- the value obtained by summing the value of the left side obtained by the relational expression (A) in (1) and the value of the left side obtained by the relational expression (B) in (7) is 250% to 420%.
- the polyolefin microporous membrane of the present invention has a narrow pore size distribution and a dense pore size, so that coating unevenness and coating wrinkles of the coating material can be greatly suppressed, and therefore can be suitably used as a coating substrate. it can. Moreover, since the intensity balance of MD direction and TD direction is adjusted, high-speed conveyance is possible. Further, since it has good permeability and withstand voltage characteristics as a substrate, it has excellent characteristics as a battery separator.
- the pore size distribution of the polyolefin microporous membrane can be measured by the following method using a porometer.
- a porometer is used for each of a dry sample (hereinafter also simply referred to as “dry sample”) and a wet sample (hereinafter also simply referred to as “wet sample”) filled with the measurement liquid in the pores.
- dry sample a dry sample
- wet sample a wet sample filled with the measurement liquid in the pores.
- FIG. 1 the relationship between the air pressure and the air flow rate is measured, and as shown in FIG. 1, the aeration curve (Dry Curve) of the dry sample and the aeration curve (Wet Curve) of the wet sample are obtained.
- the wet sample in which the measurement liquid is filled in the pores shows the same characteristics as the capillary filled with the liquid.
- the air pressure overcomes the surface tension of the measurement liquid in the pores in order from the large diameter pores, and the measurement liquid is pushed out of the pores.
- the air flow rate gradually increases, and the sample finally becomes dry.
- the shape of the pores is substantially cylindrical
- the conditions for air of pressure P to enter the pores of diameter D are that the surface tension of the measurement liquid is ⁇ and the contact angle of the measurement liquid is ⁇ . It is expressed by the Washburn formula shown in the following formula 1.
- P (4 ⁇ cos ⁇ ) / D (Formula 1) Therefore, the pore diameter can be calculated by measuring the pressure when the liquid is pushed out of the pore.
- a pore size distribution curve showing the relationship between the pore diameter D and the pore size distribution PSF can be obtained based on the pressure change of the air flow rate in the dry state and the wet state.
- An example of such a pore size distribution curve is shown in FIG.
- pore diameter distribution curve shown in FIG.
- the pore diameter indicating the mode in the pore diameter distribution curve pore diameter represented by Dp in FIG. 2; hereinafter, also simply referred to as “peak pore diameter”
- the pore diameter distribution value corresponding to the pore diameter D j pore diameter D
- D exp ⁇ ⁇ D j ⁇ (PSF) j ⁇ (Formula 4)
- the physical property values obtained from the pore size distribution curve are basically values obtained by measuring one small sample. That is, such measurement of pore size distribution is performed on a relatively small area. Therefore, in order to examine the uniformity of the pore size distribution in the entire microporous membrane in more detail, samples (measurement regions) are collected from multiple locations in the microporous membrane, and the physical property values obtained for each sample are statistically measured. It is desirable to verify the variation.
- the present inventors have found that the uniformity of the pore diameter affects the number of coating unevenness in the coating substrate.
- the gravure coating method and the blade coating method are used in the MD direction by scraping the coating material and adjusting the coating amount using blades such as a blade (doctor blade) and a knife. This is useful for a method in which a coating material is applied simultaneously in the TD direction.
- the polyolefin microporous membrane of the present invention is characterized in that the pore diameter is uniform.
- the relative value (%) (standard deviation ⁇ peak pore diameter) (variation coefficient) of the standard deviation ( ⁇ (Dexp)) of the peak pore diameter with respect to is important.
- measurement areas of arbitrary dimensions are provided at four equal intervals per 20 cm in the TD direction, and the pore size distribution is measured for each measurement area.
- a peak pore size and a distribution (Dexp) are calculated from the pore size distribution obtained in these measurement regions.
- the standard deviation ( ⁇ (Dexp)) of the distribution (Dexp) obtained in these measurement regions is calculated, and the average value (Dp) of the peak pore diameter is calculated.
- the relative value (variation coefficient B) obtained by substituting these standard deviation ( ⁇ (Dexp)) and average value (Dp) into the above-described (formula 5) is less than 24% (the following formula (A) Meeting) is important.
- the variation coefficient B is more preferably less than 19%, and further preferably less than 18%.
- the relative value is less than 24%, the variation in the hole diameter in the TD direction becomes small, and the coating material spreads uniformly on the substrate surface in the TD direction during coating. If the relative value is less than 24%, the pore diameter is uniform, so that the content of the coating material does not differ between the large and small portions of the hole diameter, and unevenness during coating is difficult to occur.
- the relative value is less than 24%, the coating material is applied uniformly, so that heat is uniformly transmitted to the base material in the TD direction in the coating material drying process, and the dry soot and the coating material are peeled off. Can be suppressed.
- dry cocoons are highly effective because the coating material unevenness in the TD direction is greatly affected. Therefore, it is important that the relative value is less than 24%. The smaller the relative value, the better because there is no variation in the pore diameter in the TD direction, but the lower limit is substantially about 5%.
- the standard deviation of the pore size distribution measured at four equal intervals per 20 cm in the TD direction is preferably less than 0.00600, more preferably less than 0.00450, More preferably, it is less than 00445. If the standard deviation of the expected value of the hole diameter in the TD direction is less than 0.00600, the hole diameter is uniform, so the content of the coating material does not differ between the large and small portions of the hole, and unevenness occurs during coating. Hard to do. Furthermore, since the coating material is applied uniformly, heat is uniformly transmitted to the base material in the coating material drying step, and drying flaws and peeling of the coating material can be suppressed.
- the lower limit of the standard deviation in the TD direction in the expected value of the hole diameter is preferably as small as possible because there is no variation in the hole diameter in the TD direction, but the lower limit is substantially about 0.00100, but less than 0.00100. There may be.
- the relative value of the standard deviation in the TD direction of the peak pore diameter with respect to the average value of the peak pore diameter measured at four equal intervals per 20 cm in the TD direction (standard deviation of the peak pore diameter ⁇ average value of the peak pore diameter) (variation coefficient A) is 5 % Is preferably less than 3%, more preferably 3% or less, and even more preferably 1% or less.
- the relative value is less than 5%, the variation in the mode value of the hole diameter distribution in the TD direction is reduced, and the hole diameter is uniform. For this reason, the content of the coating material does not differ between the portion having a large pore diameter and the portion having a small pore diameter, and unevenness is difficult to occur during coating.
- the relative value is less than 5%, the coating material is applied uniformly, so that heat is uniformly transmitted to the base material in the TD direction in the coating material drying process, and the drying wrinkles and the coating material peel off. Can be suppressed.
- dry cocoons are highly effective because the coating material unevenness in the TD direction is greatly affected. Therefore, it is important that the relative value is less than 5%. The smaller the relative value, the better because there is no variation in the pore diameter in the TD direction, but the lower limit is substantially about 0.01%.
- the uniformity of the coating material is necessary not only in a wide range but also in a narrow range. Therefore, it is necessary to make the hole diameter uniform even in a narrow width. That is, when applying the coating material to the base material, in addition to using a wide-width base material, the base material may be slit in advance narrowly in accordance with the dimensions of the separator incorporated in the actual battery. . Therefore, such a narrow product is incorporated into the battery as it is after the coating of the coating material, so it is difficult to take a countermeasure such as avoiding a site where the coating state is bad (for example, both ends in the width direction). A uniform coating film is required over the width direction.
- the calculation result (variation coefficient D) obtained by substituting the standard deviation ( ⁇ (Dexp)) and the average value (Dp) into the above-described (formula 5) is less than 24% (the above-described formula (A ) Is important.
- the variation coefficient D is more preferably less than 19%, and further preferably less than 18%.
- the relative value (coefficient of variation D) is less than 24%, the variation in the hole diameter in the TD direction becomes small, and the coating material spreads uniformly on the substrate surface in the TD direction during coating.
- the relative value (coefficient of variation D) when the relative value (coefficient of variation D) is less than 24%, the pore diameter is uniform, so the content of the coating material does not differ between the large and small portions of the pore diameter, and unevenness can occur during coating. Hateful. Further, when the relative value (coefficient of variation D) is less than 24%, the coating material is uniformly applied, so that heat is uniformly transmitted to the base material in the TD direction in the drying step of the coating material, Peeling of the coating material can be suppressed. In particular, dry cocoons are highly effective because the coating material unevenness in the TD direction is greatly affected. Therefore, it is important that the relative value is less than 24%. The smaller the relative value, the better because there is no variation in the pore diameter in the TD direction, but the lower limit is substantially about 5%.
- the standard deviation of the pore size distribution measured at 3 locations at 1 cm intervals in the TD direction is preferably less than 0.00600, more preferably less than 0.00450, and even more preferably less than 0.00445. If the standard deviation of the expected value of the hole diameter in the TD direction is less than 0.00600, the hole diameter is uniform, so the content of the coating material does not differ between the large and small portions of the hole, and unevenness occurs during coating. Hard to do. Furthermore, if the standard deviation of the expected value of the pore diameter in the TD direction is less than 0.00600, the coating material is uniformly applied, so that heat is uniformly transmitted to the base material in the coating material drying step, and the drying wrinkles , Peeling of the coating material can be suppressed. The smaller the lower limit of the standard deviation in the TD direction in the expected value of the hole diameter is, the smaller the better since there is no variation in the hole diameter in the TD direction, but the lower limit is substantially about 0.00100.
- Relative value of the standard deviation in the TD direction of the peak pore diameter (standard deviation of the peak pore diameter ⁇ average value of the peak pore diameter) (the coefficient of variation C) is less than 5% with respect to the average value of the peak pore diameter measured at 1 cm intervals in the TD direction It is preferable that it is 3% or less.
- the relative value is less than 5%, the variation in the mode value of the hole diameter distribution in the TD direction is reduced, and the hole diameter is uniform. For this reason, the content of the coating material does not differ between the portion having a large pore diameter and the portion having a small pore diameter, and unevenness is difficult to occur during coating.
- the relative value is less than 5%, the coating material is applied uniformly, so that heat is uniformly transmitted to the base material in the TD direction in the coating material drying process, and the drying wrinkles and the coating material peel off. Can be suppressed.
- dry cocoons are highly effective because the coating material unevenness in the TD direction is greatly affected. Therefore, it is important that the relative value is less than 5%. The smaller the relative value, the better because there is no variation in the pore diameter in the TD direction, but the lower limit is substantially about 0.01%.
- the standard deviation in the TD direction of the peak pore diameter measured at 3 locations at 1 cm intervals in the TD direction is preferably 0.00100 or less, more preferably 0.00070 or less, and 0.00050 or less. Further preferred. If the standard deviation of the peak pore diameter in the TD direction is 0.00100 or less, the pore diameter is uniform and the shrinkage in the width direction occurs uniformly, so that coating wrinkles can be suppressed.
- the lower limit of the standard deviation of the peak pore diameter in the TD direction is preferably as small as possible, but the lower limit is substantially about 0.00005.
- the average value of the peak pore diameter in the TD direction of the polyolefin microporous membrane is preferably 0.024 ⁇ m or less, and more preferably 0.022 ⁇ m or less.
- good withstand voltage characteristics can be obtained by reducing the pore diameter of a microporous polyolefin membrane.
- the average value of the peak pore diameter in the TD direction is preferably 0.001 or more.
- the hole diameter in the MD direction is uniform, the content of the coating material does not differ between the large and small portions of the hole, the surface unevenness can be reduced, drying unevenness can be reduced, and high-speed conveyance is possible. That is, if the pore diameter is non-uniform in the MD direction, when the coating material is applied to the surface of the base material, the coating material is absorbed at the portion where the pore diameter is large compared to other portions (portions where the pore diameter is small). Thus, there is a risk that the coating material will be insufficient at the site where the pore diameter is large. Therefore, the uniform pore size in the MD direction is also important.
- measurement areas of arbitrary dimensions are provided at three locations at 5 cm intervals in the MD direction, and the pore size distribution is measured for each measurement area.
- a peak pore size and a distribution (Dexp) are calculated from the pore size distribution obtained in these measurement regions.
- the standard deviation ( ⁇ (Dexp)) of the distribution (Dexp) obtained in these measurement regions is calculated, and the average value (Dp) of the peak pore diameter is calculated.
- the value (variation coefficient F) obtained by substituting these standard deviation ( ⁇ (Dexp)) and average value (Dp) into the above-described (formula 5) is less than 400% (satisfies formula (B)) )is important.
- the variation coefficient F is more preferably less than 330%, and even more preferably less than 320%.
- the variation coefficient F is less than 400%, the variation in the hole diameter in the MD direction is reduced, and coating unevenness in the MD direction can be suppressed. Therefore, drying unevenness at the time of high-speed conveyance can be suppressed.
- the standard deviation of the distribution measured at three locations at 5 cm intervals in the MD direction is preferably less than 0.10000, and more preferably less than 0.07000.
- Relative value of the standard deviation in the MD direction of the peak pore size (standard deviation of the peak pore size ⁇ average value of the peak pore size) relative to the average value of the peak pore size measured at 5 cm intervals in the MD direction (variation coefficient E) is less than 5% It is preferable that
- the standard deviation in the MD direction of the peak pore diameter measured at 5 locations at 5 cm intervals in the MD direction is preferably 0.00100 or less, and more preferably 0.00060 or less.
- the average value of the peak pore diameter in the MD direction of the polyolefin microporous membrane is preferably less than 0.024 ⁇ m, and more preferably 0.022 ⁇ m or less.
- the sum of the coefficient of variation B and the coefficient of variation F is preferably 450% or less.
- the sum of the coefficient of variation B and the coefficient of variation F is 450% or less, it is possible to reduce coating thickness unevenness, drying unevenness, and coating wrinkles in both the MD direction and the TD direction, and the quality of the entire film after coating is uniform. Therefore, an excellent coating substrate can be obtained.
- the sum of the coefficient of variation B and the coefficient of variation F is preferably as low as possible, but the lower limit is substantially about 50%.
- the tensile strength in the MD direction (tensile strength at break in the MD direction.
- MD tensile strength" Is preferably 4500kgf / cm 2 or less, it is 3000 kgf / cm 2 or less More preferred is 2800 kgf / cm 2 or less.
- the MD tensile strength is 4500 kgf / cm 2 or less, extreme orientation in the MD direction can be suppressed, and the microporous film can be prevented from tearing in the transport process and the winding process.
- the MD tensile strength is preferably 1600 kgf / cm 2 or more. When the MD tensile strength is 1600 kgf / cm 2 or more, high-speed conveyance at the time of coating becomes possible, and film breakage can be prevented in the winding process.
- Intensity ratio in the MD direction of the tensile strength S MD and TD directions of the tensile strength S TD S MD / S TD is preferably 1.4 or more, is 1.5 or more More preferably, it is particularly preferably 1.6 or more.
- S MD / S TD is 1.4 or more, deformation hardly occurs during winding in the MD direction.
- S MD / S TD is 1.4 or more, the tension can be easily controlled, so that the base material can be applied while maintaining a suitable tension. Good properties can be obtained as a material.
- S MD / S TD is preferably 2.5 or less, more preferably 2.2 or less, and even more preferably 1.95 or less. If the intensity ratio is 2.5 or less, only the orientation in the MD direction is suppressed from being strengthened, so that winding deviation at the time of slitting is suppressed and the slit property is improved.
- the thermal shrinkage in the MD direction when held at 105 ° C. for 8 hours is preferably 5% or less.
- the heat shrinkage rate in the MD direction when held at 105 ° C. for 8 hours is 5% or less, the microporous film can be prevented from shrinking and short-circuiting when abnormal heat is generated, and sufficient safety is ensured. I can do things.
- contraction of the base material in the drying process at the time of coating can be suppressed as the thermal contraction rate of MD direction when it hold
- the air resistance is a value measured in accordance with JIS P 8117 (2009).
- the air permeability resistance is preferably 1000 sec / 100 cc or less, more preferably 800 sec / 100 cc or less, and further preferably 500 sec / 100 cc.
- the air resistance is preferably 100 sec / 100 cc or more.
- the air resistance is 100 sec / 100 cc or more, good strength can be obtained.
- the permeability is deteriorated by making the pore diameter fine (the pore diameter is small and the distance between adjacent pore diameters is small), but the microporous membrane obtained by the present invention Is excellent in that it has good permeability despite having a uniform and small pore size (a fine pore size). Thereby, when it uses as a separator, a favorable output characteristic is acquired.
- the withstand voltage (dielectric breakdown voltage) when the film thickness is 20 ⁇ m is preferably 2.4 kV or more, and preferably 2.6 kV or more, from the viewpoint of insulating properties of the separator. More preferred.
- the withstand voltage when the film thickness is 20 ⁇ m means that the dielectric breakdown voltage in the microporous film having the film thickness T 1 ( ⁇ m) is V 1 (kV):
- V 2 (V 1 ⁇ refers to the breakdown voltage V 2 calculated by 20) / T 1, when the measurement was performed a plurality of times shall refer to their mean values.
- the withstand voltage and the pore diameter are deeply related.
- the microporous membrane obtained by the present invention is superior to the conventional microporous membrane in that it has fine permeability and voltage resistance despite being fine and uniform pore size.
- puncture strength is used in the meaning of “puncture strength when the thickness is 20 ⁇ m” unless otherwise specified.
- the puncture strength is preferably 450 gf or more. When the puncture strength is 450 gf or more, pinholes and cracks that are generated when sharp portions such as electrode materials pierce the microporous film can be suppressed, and the defect rate during battery assembly can be reduced.
- the coating layer may be peeled off during high-speed conveyance, leading to contamination in the coating layer.
- the upper limit of the porosity of the polyolefin microporous membrane of the present invention is preferably 70%, more preferably 60%.
- the lower limit of the porosity is preferably 20%, more preferably 40%.
- the content of the polyolefin component having a large molecular weight is large from the viewpoint of membrane strength.
- the content of the polyolefin component having a molecular weight of 1,000,000 or more is preferably 20% by weight or more, and more preferably 25% by weight or more.
- polyethylene constituting the polyolefin microporous membrane of the present invention
- polyethylene it is preferable to use polyethylene.
- the polyethylene content is preferably 90% by weight or more, more preferably 95% by weight or more, and particularly preferably 99% by weight or more, based on 100% by weight of the entire polyolefin.
- polyethylene has a polyethylene component with a molecular weight of 500,000 or less and a polyethylene component with a molecular weight of 1,000,000 or more.
- Polyolefins other than polyethylene may include polypropylene and copolymer polyolefin.
- FIG. 3 shows a relationship diagram of the molecular weight distribution curve of polyethylene obtained by GPC.
- the horizontal axis represents the logarithmic value of molecular weight
- the vertical axis represents the value obtained by differentiating the concentration fraction of polyethylene with the logarithmic value of molecular weight.
- the region (a) corresponds to “a polyethylene component having a molecular weight of 500,000 or less”
- the region (b) corresponds to “a polyethylene component having a molecular weight of 1 million or more”.
- the content of the polyethylene component having a molecular weight of 500,000 or less is preferably 70% by weight or less, more preferably 65% by weight or less, and 60% by weight or less, based on 100% by weight of the entire polyethylene. Is particularly preferred. When the content of the polyethylene component having a molecular weight of 500,000 or less is 70% by weight or less, a decrease in strength of the microporous film can be suppressed.
- the content of a polyethylene component having a molecular weight of 1 million or more is preferably 20% by weight or more, and more preferably 25% by weight or more, based on 100% by weight of the entire polyethylene.
- the molecular weight of polyethylene is important in order to obtain a uniform and dense pore diameter when the stretching process is a two-stage process including a uniaxial stretching process and a simultaneous biaxial stretching process as described later. It becomes.
- the content of low molecular weight polyethylene is high or when the content of high molecular weight polyethylene is low, the entanglement of polyethylene molecules is weak, and when uniaxial stretching is performed, strong and weak parts of the polyethylene molecule are entangled. .
- the hole diameter becomes non-uniform at the stage of the simultaneous biaxial stretching process in which the holes are opened (the variation in the hole diameters increases), making it difficult to control the hole diameter.
- the entanglement of the polyethylene molecules can be sufficiently ensured, so that the draw ratio of uniaxial stretching can be increased, and the MD remains uniform and has a small pore diameter.
- the strength of the direction can be increased. From the above, it is preferable that the polyethylene component having a molecular weight of 500,000 or less is 70% or less and the polyethylene component having a molecular weight of 1 million or more is 20% or more.
- polyethylene as a material for the microporous membrane is polyethylene having a weight average molecular weight of 5.0 ⁇ 10 5 to 9.0 ⁇ 10 5 (high density polyethylene; hereinafter, also simply referred to as “HDPE”). And a composition with polyethylene having a weight average molecular weight of 1.5 ⁇ 10 6 to 3.0 ⁇ 10 6 (ultra high molecular weight polyethylene; hereinafter also simply referred to as “UHMWPE”).
- HDPE high density polyethylene
- UHMWPE ultra high molecular weight polyethylene
- the molecular weight distribution (Mw / Mn) of both HDPE and UHMWPE is preferably 3 or more.
- Mw / Mn the molecular weight distribution of both HDPE and UHMWPE.
- the molecular weight distribution is preferably 20 or less for both HDPE and UHMWPE. When the molecular weight distribution is 20 or less, a decrease in strength due to an increase in low molecular weight components can be suppressed.
- the method for producing a microporous polyolefin membrane of the present invention uses a so-called wet method, and includes a step of stretching in a uniaxial direction and a step of performing simultaneous biaxial stretching in this order in a state where a solvent and a solute (polyolefin) are mixed. It is important that By performing stretching in the uniaxial direction in a state where the solvent and the solute are mixed, it becomes possible to control the anisotropy in the stretching direction and to refine the pore structure. Thereby, the characteristic outstanding as a base material for coating is acquired.
- the microporous membrane produced by the above process has a uniform and small pore diameter, and has a good strength balance in the MD and TD directions, permeability, and withstand voltage characteristics. Therefore, the following (1), (2 It is important to be manufactured by the process of (1) A step of stretching the sheet extruded from the die in the MD direction at a stretching temperature of 90 to 115 ° C. and a stretching ratio of 1.4 to 2.0 times. (2) A sheet stretched in the MD direction is stretched at a stretching temperature. Step of simultaneously stretching in the MD direction and TD direction at 100 to 120 ° C.
- a membrane can be obtained.
- the molecular chains are in an appropriately entangled state.
- the step (2) in this state, a microporous film having no uneven pore size distribution in the TD direction can be obtained, and the pore size can be densified.
- the draw ratio in the step (1) is too high, the entanglement balance between the molecular chains is lost, and when the MD direction is stretched, the variation in the pore diameter in the TD direction tends to increase.
- the draw ratio in the step (1) is important to be 1.4 times or more.
- the draw ratio in the MD direction is preferably 2.0 times or less.
- the draw ratio in the MD direction is 2.0 times or less, the degree of orientation in the MD direction can be adjusted, and the microporous membrane can be prevented from tearing in the transport process and the winding process.
- the draw ratio in the MD direction is 2.0 times or less, the hole diameter distribution unevenness in the TD direction can be suppressed, and a uniform hole diameter free from the hole diameter distribution unevenness can be obtained.
- the stretching ratio in the step (2) is preferably 16 times or more and more preferably 25 times or more in terms of area magnification.
- the area magnification in the step (2) is 16 times or more, there is no uneven stretching of the film and uniform stretching is possible, and uneven physical properties and uneven pore size distribution can be suppressed.
- the area magnification in the step (2) is preferably 49 times or less. When the area magnification in the step (2) is 49 times or less, membrane breakage due to an increase in the total area magnification can be suppressed, and productivity is improved.
- the stretching in the step (2) is preferably simultaneous stretching at the same magnification in the TD direction and the MD direction.
- the polyolefin microporous membrane of the present invention can be suitably used as a coating substrate. Therefore, the coating layer preferably applied to the present invention will be described next.
- the coating layer applied to this invention contains water-soluble resin or water-dispersible resin, and microparticles
- the solvent used for the coating material includes not only a liquid that dissolves the water-soluble resin or water-dispersible resin, but also broadly includes a dispersion medium that is used to disperse the water-soluble resin or water-dispersible resin in the form of particles.
- water is the main component.
- the water used is preferably ion exchange water or distilled water.
- the solvent may be water alone, but a water-soluble organic solvent such as alcohols can be used as necessary. By using these water-soluble organic solvents, the drying rate and coating property can be improved.
- the coating layer may contain a surfactant, an antistatic agent, etc. as a composition other than the water-soluble resin or water-dispersible resin and fine particles as long as the object of the present invention is not impaired.
- the fine particles may be inorganic particles or organic particles.
- the shape of the particle may be a true spherical shape, a substantially spherical shape, a plate shape, or a needle shape, but is not particularly limited.
- Examples of methods for applying the coating material include reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, Mayer bar coating method, pipe doctor method, blade coating method. Method, die coating method and the like, and these methods can be carried out singly or in combination.
- a method of simultaneously applying a coating material in the TD direction using a blade or knife such as a gravure coating method or a blade coating method is preferably applied to the polyolefin microporous membrane of the present invention. The solvent is generally removed by drying.
- the present invention provides a coating substrate using the above-mentioned polyolefin microporous membrane. Since such a coating substrate is controlled to have a uniform pore size and a small pore size, the coating material can be uniformly applied while suppressing problems such as coating unevenness, peeling of the coating material, and generation of wrinkles. The quality of the coated product is improved. Furthermore, since the tensile strength in the MD direction is high and the balance between the MD tensile strength and the TD tensile strength is excellent, a high tension can be applied during coating. Therefore, it is also suitable for high-speed coating. Moreover, it is excellent in that it has both a small pore size and a uniform pore size, good permeability, and withstand voltage characteristics, and is also excellent as a battery separator.
- Pore size distribution standard deviation in MD or TD direction
- the pore size distribution (Dexp) was calculated as follows. Four samples with a diameter of 3 cm at intervals of 5 cm (distance between the centers of the circles) along the TD direction of the microporous film, and samples with a diameter of 3 cm at intervals of 3 cm (distance between the centers of the circles) along the TD direction. Three samples having a diameter of 3 cm were collected at intervals of 5 cm in the MD direction (distance between the centers of the circles). Since these samples were collected in different areas, a total of 10 samples were obtained.
- the pore size distribution of the obtained sample was measured in a measurement pressure range of 0 to 3500 MPa using a palm porometer (model number: CFP-1500A, measurement solution: Galwick) manufactured by PMI, and then the pore size distribution of each sample.
- (Dexp) was calculated based on Equation 4 above. And about four measurement samples extract
- Peak pore diameter, average value and standard deviation in the TD direction The peak pore diameter was calculated as follows. Four samples with a diameter of 3 cm at intervals of 5 cm (distance between the centers of the circles) along the TD direction of the microporous film, and samples with a diameter of 3 cm at intervals of 3 cm (distance between the centers of the circles) along the TD direction. Three samples having a diameter of 3 cm were collected at intervals of 5 cm in the MD direction (distance between the centers of the circles). Since these samples were collected in different areas, a total of 10 samples were obtained.
- each obtained sample it measured in the range of measurement pressure 0-3500MPa using the palm porometer (model number: CFP-1500A, measurement liquid: Galwick) made from PMI, and peak pore diameter (pore diameter in the mode value) Asked. And about four measurement samples extract
- HT-GPC manufactured by Polymer Laboratories, PL-220
- Detector Differential refractive index detector RI Guard column: Shodex G-HT Column: Shodex HT806M (2 pieces) ( ⁇ 7.8 mm ⁇ 30 cm, Showa Denko)
- Solvent 1,2,4-trichlorobenzene (TCB, Wako Pure Chemical Industries) (0.1% BHT added)
- Flow rate 1.0 mL / min
- Sample preparation 5 mL of the measurement solvent was added to 5 mg of the sample, and the mixture was heated and stirred at 160 to 170 ° C. for about 30 minutes, and then the resulting solution was filtered through a metal filter (pore size: 0.5 ⁇ m).
- Injection volume 0.200 mL
- Standard sample monodisperse polystyrene (manufactured by Tosoh)
- Data processing TRC GPC data processing system
- Calibration curve Calculated from a calibration curve obtained using a monodisperse polystyrene standard sample using a predetermined conversion constant. Based on the curve obtained by the above test, the areas of components having a molecular weight of 500,000 or less and components having a molecular weight of 1,000,000 or more were calculated. Then, the ratio with respect to the total area of a component with a molecular weight of 500,000 or less and a component with a molecular weight of 1,000,000 or more was obtained.
- Film thickness The thickness of the microporous film was measured at a randomly selected MD position using a contact-type thickness meter. Measurements were made at 5 mm intervals over a distance of 30 cm along the TD direction of the membrane. And the measurement along the said TD direction was performed 5 times in different MD positions, and the arithmetic average was made into the thickness of the sample.
- Thermal shrinkage in the MD direction The microporous membrane was cut into 5 cm ⁇ 5 cm, and the shrinkage in the MD direction was measured 3 times (measured for 3 samples) when treated at 105 ° C. for 8 hours (non-fixed). The average value was taken as the thermal shrinkage in the MD direction.
- CMC Carboxymethylcellulose
- solvent water 60.8% by weight
- 38.4 parts by mass of substantially spherical alumina fine particles having an average particle diameter of 0.5 ⁇ m were added and stirred for 2 hours to sufficiently disperse the alumina fine particles, and then the filtration particle size (initial filtration efficiency: 95%) was 10 ⁇ m.
- the volume ratio of the resin component to the fine particles was 5:95 (calculated assuming a specific gravity of CMC of 1.6 g / cm 3 and a specific gravity of alumina of 4.0 g / cm 3 ).
- a sample of 15 cm ⁇ 10 cm in size is randomly collected and visually checked for coating unevenness. went. Specifically, a transmission type light is used, and a portion of the sample that is different in color from the other portion is coated with light, and coating unevenness is determined. After calculating the work unevenness area ratio, a determination was made based on the following criteria.
- Coating unevenness area ratio (%) (area of unevenness / total area (15 ⁇ 10 cm)) ⁇ 100 (Equation 6) ⁇ Criteria for coating unevenness> Coating uneven area ratio 0 to 1%: ⁇ (best) Coating unevenness area ratio 1-2%: ⁇ (excellent) Coating uneven area ratio 2-6%: ⁇ (good) Coating uneven area ratio 6% or more: ⁇ (impossible) If the coating unevenness area ratio is 2% or less, there is no practical problem.
- the coating liquid obtained was coated on the microporous membrane by hand coating and dried at 70 ° C for 1 minute, and then a sample of 15cm x 10cm size was randomly collected and visually confirmed for the number of wrinkles did.
- Judgment criteria are as follows. Number of cocoons 0-1: ⁇ (best) Number of cocoons 2-3: ⁇ (excellent) Number of cocoons 4-7: ⁇ (good) Number of cocoons 8 or more: ⁇ (impossible) If the number of ridges is 3 or less, there is no practical problem.
- Example 1 30% by weight of ultra high molecular weight polyethylene (UHMWPE (PE1)) having a weight average molecular weight (Mw) of 2.89 ⁇ 10 6 and a molecular weight distribution Mw / Mn of 5.28, and a weight average molecular weight Mw of 5.72 ⁇ a 10 5, high density polyethylene (HDPE (PE2)) molecular weight distribution Mw / Mn is 4.81 was prepared polyethylene composition consisting of 70 wt%. When the entire polyethylene composition was 100% by weight, the content of polyethylene component having a molecular weight of 500,000 or less was 59% by weight, and the content of polyethylene component having a molecular weight of 1 million or more was 26% by weight.
- UHMWPE ultra high molecular weight polyethylene
- PE2 high density polyethylene
- Example 2 A polyolefin microporous membrane was produced in the same manner as in Example 1 except that MD stretching and simultaneous biaxial stretching were performed at a stretching temperature of 110 ° C. Table 1 shows the film characteristics of the obtained polyolefin microporous film.
- Example 3 A polyolefin microporous membrane was produced in the same manner as in Example 1 except that the draw ratio in the MD stretching step was 1.8 times. Table 1 shows the film characteristics of the obtained polyolefin microporous film.
- Example 4 A polyolefin microporous membrane was prepared in the same manner as in Example 1 except that the amount ratio of PE1 and PE2 was 20/80. When the entire polyethylene composition was 100% by weight, the content of polyethylene component having a molecular weight of 500,000 or less was 64% by weight, and the content of polyethylene component having a molecular weight of 1 million or more was 20% by weight. Table 1 shows the film characteristics of the obtained polyolefin microporous film.
- Example 5 A polyolefin microporous membrane was prepared in the same manner as in Example 1 except that the stretching ratio in the MD stretching step was 2.0. Table 1 shows the film characteristics of the obtained polyolefin microporous film.
- Example 1 A polyolefin microporous membrane was prepared in the same manner as in Example 1 except that the amount ratio of PE1 and PE2 was changed to 10/90.
- the entire polyethylene composition was 100% by weight, the content of the polyethylene component having a molecular weight of 500,000 or less was 70% by weight, and the content of the polyethylene component having a molecular weight of 1 million or more was 14% by weight.
- Table 2 shows the membrane characteristics of the obtained polyolefin microporous membrane.
- Example 2 A polyolefin microporous membrane was prepared in the same manner as in Example 1 except that the stretching ratio in the MD stretching step was 1.3 times. Table 2 shows the membrane characteristics of the obtained polyolefin microporous membrane.
- Example 3 A polyolefin microporous membrane was prepared in the same manner as in Example 1 except that the MD stretching step was not performed and only the simultaneous biaxial stretching step was performed as the stretching step. Table 2 shows the membrane characteristics of the obtained polyolefin microporous membrane.
- Comparative Example 4 A polyolefin microporous membrane was produced in the same manner as in Comparative Example 3 except that the draw ratio in the simultaneous biaxial stretching step was 7 ⁇ 5 times. Table 2 shows the membrane characteristics of the obtained polyolefin microporous membrane.
- microporous membrane according to the present invention can be suitably used as a coating substrate having a great demand in the fields of battery separators, capacitor films, filters and the like.
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Abstract
Description
(1)孔径の分布を測定するための測定領域をTD方向に沿って互いに離間させて複数設定した時に、これら測定領域にてそれぞれ得られた測定結果が以下の関係式(A)を満たすことを特徴とするポリオレフィン微多孔膜。
σ(Dexp)÷Dp×100<24 ・・・・・(A)
ただし、σ(Dexp)はそれぞれの測定領域について以下の式で算出されるDexpを用いて計算した標準偏差であり、Dpはそれぞれの測定領域にて得られた孔径分布の最頻値(孔径)を平均した値である。
Dexp=Σ{Dj×(PSF)j}
(Dj:孔径、(PSF)j:孔径分布の値(孔径Djの頻度)
(2)前記測定領域は、TD方向において20cmあたり4か所等間隔に設けられていることを特徴とする(1)に記載のポリオレフィン微多孔膜。
(3)前記σ(Dexp)が0.00600未満である、(2)に記載のポリオレフィン微多孔膜。
(4)前記σ(Dexp)が0.00100未満である、(2)に記載のポリオレフィン微多孔膜。
(5)前記Dpが0.010~0.024μmである、(1)~(4)のいずれかに記載のポリオレフィン微多孔膜。
(6)前記測定領域は、TD方向に1cm間隔で3か所設けられていることを特徴とする(1)に記載のポリオレフィン微多孔膜。
(7)孔径の分布を測定するための測定領域をMD方向に沿って互いに離間させて複数設定した時に、これら測定領域にてそれぞれ得られた測定結果が以下の関係式(B)を満たすことを特徴とするポリオレフィン微多孔膜。
σ(Dexp)÷Dp×100<400 ・・・・・(B)
ただし、σ(Dexp)はそれぞれの測定領域について以下の式で算出されるDexpを用いて計算した標準偏差であり、Dpはそれぞれの測定領域にて得られた孔径分布の最頻値(孔径)を平均した値である。
Dexp=Σ{Dj×(PSF)j}
(Dj:孔径、(PSF)j:孔径分布の値(孔径Djの頻度))
(8)前記測定領域は、MD方向において5cm間隔で3か所設けられていることを特徴とする(7)に記載のポリオレフィン微多孔膜。
(9)前記Dpが0.010~0.024μmである、(7)または(8)に記載のポリオレフィン微多孔膜。
(10)(1)の関係式(A)にて得られた左辺の値と、(7)の関係式(B)にて得られた左辺の値とを合計した値が250%~420%であるポリオレフィン微多孔膜。
(11)MD方向の引張り強度が1600~4500kgf/cm2である、(1)~(10)のいずれかに記載のポリオレフィン微多孔膜。
(12)MD方向の引張り強度とTD方向の引張り強度の比が1.4~2.5である、(1)~(11)のいずれかに記載のポリオレフィン微多孔膜。
(13)分子量1.0×106以上のポリオレフィンの含有量が20重量%以上である、(1)~(12)のいずれかに記載のポリオレフィン微多孔膜。
(14)(1)~(13)のいずれかに記載のポリオレフィン微多孔膜を用いてなるコーティング用基材。
P=(4γcosθ)/D ……(式1)
従って、液体がその細孔から押し出される際の圧力を測定することによって、細孔直径を算出できる。
CFF=[(Fw,j/Fd,j)×100] ……(式2)
PSF=(CFF)j+1-(CFF)j ……(式3)
Dexp=Σ{Dj×(PSF)j} ……(式4)
均一塗工を行うためには、ポリオレフィン微多孔膜の孔径の分布(Dexp)及びピーク孔径をMD方向又はTD方向に互いに離間させて複数測定した際に得られる、ピーク孔径の平均値(Dp)に対するピーク孔径の標準偏差(σ(Dexp))の相対値(%)(標準偏差÷ピーク孔径)(変動係数)が重要である。前記相対値は以下の式により求められる。
相対値(%)=σ(Dexp)÷ Dp×100 ……(式5)
σ(Dexp)÷Dp×100<24 ・・・・・式(A)
更に前記変動係数Bは、19%未満であることがより好ましく、18%未満であることがさらに好ましい。当該相対値が24%未満であると、TD方向における孔径のバラつきが小さくなり、塗工時に塗材がTD方向に均一に基材表面にいきわたる。また、当該相対値が24%未満であると、孔径が均一であるため、孔径の大きい部分、小さい部分で塗材の含有量が異なることがなく、塗工時にムラができにくい。さらに、当該相対値が24%未満であると、塗材が均一に塗工されるため、塗材の乾燥工程において基材にTD方向に均一に熱が伝わり、乾燥皺、塗材のはがれを抑制できる。特に、乾燥皺はTD方向の塗材ムラが大きく影響するため、その効果が大きい。そのため、相対値が24%より小さいことが重要である。この相対値は小さければ小さいほどTD方向の孔径のバラつきがないため好ましいが、実質的に下限は5%程度である。
σ(Dexp)÷Dp×100<400 ・・・・・式(B)
変動係数Fは、330%未満であることがより好ましく、320%未満であることがさらに好ましい。変動係数Fが400%未満であるとMD方向における孔径のバラつきが小さくなり、MD方向の塗工ムラを抑制できる。そのため、高速搬送時の乾燥ムラを抑制できる。
(1)ダイから押し出されたシートを、延伸温度90~115℃、延伸倍率1.4~2.0倍にてMD方向に延伸する工程
(2)MD方向に延伸されたシートを、延伸温度100~120℃にてMD方向およびTD方向に同時延伸する工程
製造時に上記工程を実施することにより、従来の製造方法により製造された、延伸倍率が同程度のポリオレフィン微多孔膜と比較して、より緻密かつ均一な孔径が得られ、さらに良好なMD方向とTD方向の強度バランス及び透過性、耐電圧特性が得られる。これにより、コーティング用基材として優れた特性を有する本発明のポリオレフィン微多孔膜を得ることができる。
1.孔径分布、そのMDまたはTD方向における標準偏差
孔径の分布(Dexp)を、以下のようにして算出した。微多孔膜のTD方向に沿って、5cm間隔(円の中心間距離)にて直径3cmの試料を4個、TD方向に沿って3cm間隔(円の中心間距離)にて直径3cmの試料を3個、MD方向に5cm間隔(円の中心間距離)にて直径3cmの試料を3個採取した。なお、これら試料は互いに異なる領域にて採取したため、合計10個の試料が得られている。
得られた試料の細孔径分布を、PMI社製のパームポロメータ(型番:CFP-1500A、測定液:Galwick)を用いて測定圧力0~3500MPaの範囲で測定した後、各試料の孔径の分布(Dexp)を上述の式4に基づいて算出した。そして、TD方向に沿って5cm間隔(円の中心間距離)にて採取した4個の測定試料について、更にはTD方向に沿って3cm間隔(円の中心間距離)にて採取した3個の測定試料について、あるいはMD方向に5cm間隔(円の中心間距離)にて採取した3個の測定試料について、分布の標準偏差をそれぞれ算出した。これら標準偏差を「孔径の分布のMD(またはTD)方向における標準偏差(σ(Dexp))」とした。
ピーク孔径は、以下のようにして算出した。微多孔膜のTD方向に沿って、5cm間隔(円の中心間距離)にて直径3cmの試料を4個、TD方向に沿って3cm間隔(円の中心間距離)にて直径3cmの試料を3個、MD方向に5cm間隔(円の中心間距離)にて直径3cmの試料を3個採取した。なお、これら試料は互いに異なる領域にて採取したため、合計10個の試料が得られている。
得られた各試料について、PMI社製のパームポロメータ(型番:CFP-1500A、測定液:Galwick)を用いて測定圧力0~3500MPaの範囲で測定し、ピーク孔径(最頻値における孔径)を求めた。そして、TD方向に沿って5cm間隔(円の中心間距離)にて採取した4個の測定試料について、更にはTD方向に沿って3cm間隔(円の中心間距離)にて採取した3個の測定試料について、あるいはMD方向に5cm間隔(円の中心間距離)にて採取した3個の測定試料について、ピーク孔径の平均値および標準偏差をそれぞれ算出し、それぞれ「ピーク孔径のMD(またはTD)方向における平均値」及び「ピーク孔径のMD(またはTD)方向における標準偏差」とした。
高温GPCによりポリオレフィンの分子量分布測定(重量平均分子量、分子量分布、所定成分の含有量などの測定)を行った。測定条件は以下の通りであった。
装置:高温GPC装置 (機器No. HT-GPC、Polymer Laboratories製、PL-220)
検出器:示差屈折率検出器RI
ガードカラム:Shodex G-HT
カラム:Shodex HT806M(2本) (φ7.8mm×30cm、昭和電工製)
溶媒:1,2,4-トリクロロベンゼン(TCB、和光純薬製)(0.1% BHT添加)
流速:1.0mL/min
カラム温度:145℃
試料調製:試料5mgに測定溶媒5mLを添加し、160~170℃で約30分加熱攪拌した後、得られた溶液を金属フィルター(孔径0.5μm)にてろ過した。
注入量:0.200mL
標準試料:単分散ポリスチレン(東ソー製)
データ処理:TRC製GPCデータ処理システム
検量線:単分散ポリスチレン標準試料を用いて得られた検量線から所定の換算定数を用いて算出した。
上記試験により得られたカーブをもとに分子量50万以下の成分及び分子量100万以上の成分の面積を算出した。その後、それぞれ分子量50万以下の成分と分子量100万以上の成分の総面積に対する割合を求めた。
微多孔膜の厚みは、接触式厚さ計を用いて、無作為に選択したMD位置で測定した。測定は、膜のTD方向に沿って、30cmの距離にわたって5mmの間隔で行った。そして、上記TD方向に沿った測定を異なるMD位置で5回行い、その算術平均を試料の厚さとした。
膜厚T1の微多孔膜に対して透気度計(旭精工株式会社製、EGO-1T)を用いJIS-P8117記載の方法で透気抵抗度P1を測定し、式:P2=(P1×20)/T1
により、膜厚を20μmとしたときの透気抵抗度P2を算出した。
先端に球面(曲率半径R:0.5mm)を有する直径1mmの針を、平均膜厚T1(μm)の微多孔膜に2mm/秒の速度で突刺して最大荷重L1(貫通する直前の荷重、単位:gf)を測定し、L2=(L1×20)/T1の式により、膜厚を20μmとしたときの突刺強度L2(gf/20μm)を算出した。
空孔率は、微多孔膜の質量w1と、微多孔膜と同じポリエチレン組成物からなる同サイズの空孔のない膜の質量w2から、空孔率(%)=(w2-w1)/w2×100の式により算出した。
微多孔膜を5cm×5cmに切り出し、105℃にて8時間処理(非固定)したときのMD方向における収縮率を3回測定し(3個の試料について測定し)、それらの平均値をMD方向の熱収縮率とした。
MD引張り強度およびTD引張り強度については、それぞれ幅10mmの短冊状試験片を用いて、ASTM D882に準拠した方法により測定した。
150mm四方のアルミニウム製の板上に、直径60mmに切り出した膜厚T1の微多孔膜を置き、その上に真鍮製の直径50mmの円柱電極を置いて、菊水電子工業製TOS5051A耐電圧試験器を接続した。0.2kV/秒の昇圧速度で電圧を加えていって、絶縁破壊したときの値V1を読み取り、換算式:V2=(V1×20)/T1に基づいて、膜厚20μmあたりの耐電圧V2を算出した。耐電圧V2の測定は3回行い、平均値を得た。
カルボキシメチルセルロース(CMC)(ダイセルファインケム株式会社製、品番2200)0.8wt%に溶媒(水)60.8wt%を加え、2時間攪拌した。続いて平均粒径0.5μmの略球形状のアルミナ微粒子を38.4質量部加え、2時間攪拌してアルミナ微粒子を十分分散させた後、濾過粒子サイズ(初期濾過効率:95%)が10μmのフェルト型ポリプロピレン製フィルターで精密濾過し、塗布液とした。この時、樹脂成分と微粒子の体積比は5:95であった(CMCの比重1.6g/cm3、アルミナの比重4.0g/cm3として計算した。)。
得られた塗布液をハンドコートにより微多孔膜上にコーティングし、70℃で1分乾燥した後、15cm×10cmの大きさのサンプルを無作為に採取し、塗工ムラの有無について目視確認を行った。具体的には、透過型ライトを用い、採取したサンプルにライトを当て色味が他の部分と比べて異なる部分を塗工ムラとし、採取したサンプルとムラ部分の面積比から下記式6により塗工ムラ面積比を算出した後、下記判定基準に基づいて判断を行った。
塗工ムラ面積比(%)=(ムラ部分の面積/総面積(15×10cm))×100……(式6)
<塗工ムラの判定基準>
塗工ムラ面積比0~1%:◎(最良)
塗工ムラ面積比1~2%:○(優)
塗工ムラ面積比2~6%:△(良)
塗工ムラ面積比6%以上:×(不可)
なお、塗工ムラ面積比が2%以下であれば実用上問題ない。
得られた塗布液をハンドコートにより微多孔膜上にコーティングし、70℃で1分乾燥した後、15cm×10cmの大きさのサンプルを無作為に採取し目視により皺の数を確認した。判定基準は以下の通りである。
皺の数0~1個:◎(最良)
皺の数2~3個:○(優)
皺の数4~7個:△(良)
皺の数8個以上:×(不可)
なお、皺の数が3個以下であれば実用上問題ない。
重量平均分子量(Mw)が2.89×106であり、分子量分布Mw/Mnが5.28である超高分子量ポリエチレン(UHMWPE(PE1))30重量%と、重量平均分子量Mwが5.72×105であり、分子量分布Mw/Mnが4.81である高密度ポリエチレン(HDPE(PE2))70重量%とからなるポリエチレン組成物を準備した。このポリエチレン組成物全体を100重量%としたとき、分子量50万以下のポリエチレン成分の含有量は59重量%であり、分子量100万以上のポリエチレン成分の含有量は26重量%であった。このポリエチレン組成物28.5重量%に流動パラフィン71.5重量%を加え、さらに、混合物中のポリエチレンの質量を基準として0.5質量%の2,6-ジ-t-ブチル-p-クレゾールと0.7質量%のテトラキス〔メチレン-3-(3,5-ジ-t-ブチル-4-ヒドロキシルフェニル)-プロピオネート〕メタンを酸化防止剤として加えて混合し、ポリエチレン樹脂溶液を調製した。このポリエチレン樹脂溶液を、二軸スクリュー押出機からTダイに供給し、厚さ約1.0mmのシート状に押し出した後、押出物を25℃に制御された冷却ロールで冷却してゲル状シートを形成した。得られたゲル状シートを115℃の温度にさらしながら、バッチタイプの延伸機を用いて延伸倍率1.4倍にてMD方向に延伸するMD延伸工程を実施した後、115℃の温度にさらしながら、さらにMD方向およびTD方向の両方に5×5の倍率にて同時二軸延伸を行う同時二軸延伸工程を実施した。延伸されたシートを20cm×20cmのアルミニウムフレームプレートに固定し、塩化メチレンの洗浄浴に浸漬し、10分間揺らしながら洗浄して流動パラフィンを除去した後、洗浄した膜を室温で空気乾燥させた。そして、膜を125℃で10分間保持し、ポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表1に示す。
MD延伸、同時二軸延伸を延伸温度110℃とした他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表1に示す。
MD延伸工程における延伸倍率を1.8倍とした他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表1に示す。
PE1とPE2の量比を20/80とした他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。このポリエチレン組成物全体を100重量%としたとき、分子量50万以下のポリエチレン成分の含有量は64重量%であり、分子量100万以上のポリエチレン成分の含有量は20重量%であった。得られたポリオレフィン微多孔膜の膜特性を表1に示す。
MD延伸工程における延伸倍率を2.0倍とした他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表1に示す。
PE1とPE2の量比を10/90とした他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。このポリエチレン組成物全体を100重量%としたとき、分子量50万以下のポリエチレン成分の含有量は70重量%であり、分子量100万以上のポリエチレン成分の含有量は14重量%であった。得られたポリオレフィン微多孔膜の膜特性を表2に示す。
MD延伸工程における延伸倍率を1.3倍とした他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表2に示す。
MD延伸工程を行わず、延伸工程として同時二軸延伸工程のみを実施した他は、実施例1と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表2に示す。
同時二軸延伸工程の延伸倍率を7×5倍とした他は、比較例3と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表2に示す。
同時二軸延伸工程の延伸倍率を6×6倍とした他は、比較例3と同様にしてポリオレフィン微多孔膜を作製した。得られたポリオレフィン微多孔膜の膜特性を表2に示す。
Claims (14)
- 孔径の分布を測定するための測定領域をTD方向に沿って互いに離間させて複数設定した時に、これら測定領域にてそれぞれ得られた測定結果が以下の関係式(A)を満たすことを特徴とするポリオレフィン微多孔膜。
σ(Dexp)÷Dp×100<24 ・・・・・(A)
ただし、σ(Dexp)はそれぞれの測定領域について以下の式で算出されるDexpを用いて計算した標準偏差であり、Dpはそれぞれの測定領域にて得られた孔径分布の最頻値(孔径)を平均した値である。
Dexp=Σ{Dj×(PSF)j}
(Dj:孔径、(PSF)j:孔径分布の値(孔径Djの頻度)) - 前記測定領域は、TD方向において20cmあたり4か所等間隔に設けられていることを特徴とする請求項1に記載のポリオレフィン微多孔膜。
- 前記σ(Dexp)が0.00600未満である、請求項2に記載のポリオレフィン微多孔膜。
- 前記σ(Dexp)が0.00100未満である、請求項2に記載のポリオレフィン微多孔膜。
- 前記Dpが0.010~0.024μmである、請求項1~4のいずれかに記載のポリオレフィン微多孔膜。
- 前記測定領域は、TD方向に1cm間隔で3か所設けられていることを特徴とする請求項1に記載のポリオレフィン微多孔膜。
- 孔径の分布を測定するための測定領域をMD方向に沿って互いに離間させて複数設定した時に、これら測定領域にてそれぞれ得られた測定結果が以下の関係式(B)を満たすことを特徴とするポリオレフィン微多孔膜。
σ(Dexp)÷Dp×100<400 ・・・・・(B)
ただし、σ(Dexp)はそれぞれの測定領域について以下の式で算出されるDexpを用いて計算した標準偏差であり、Dpはそれぞれの測定領域にて得られた孔径分布の最頻値(孔径)を平均した値である。
Dexp=Σ{Dj×(PSF)j}
(Dj:孔径、(PSF)j:孔径分布の値(孔径Djの頻度)) - 前記測定領域は、MD方向において5cm間隔で3か所設けられていることを特徴とする請求項7に記載のポリオレフィン微多孔膜。
- 前記Dpが0.010~0.024μmである、請求項7または8に記載のポリオレフィン微多孔膜。
- 請求項1の関係式(A)にて得られた左辺の値と、請求項7の関係式(B)にて得られた左辺の値とを合計した値が250%~420%であるポリオレフィン微多孔膜。
- MD方向の引張り強度が1600~4500kgf/cm2である、請求項1~10のいずれかに記載のポリオレフィン微多孔膜。
- MD方向の引張り強度とTD方向の引張り強度の比が1.4~2.5である、請求項1~11のいずれかに記載のポリオレフィン微多孔膜。
- 分子量1.0×106以上のポリオレフィンの含有量が20重量%以上である、請求項1~12のいずれかに記載のポリオレフィン微多孔膜。
- 請求項1~13のいずれかに記載のポリオレフィン微多孔膜を用いてなるコーティング用基材。
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Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000044709A (ja) * | 1998-07-27 | 2000-02-15 | Nitto Denko Corp | 多孔質フィルムの製造方法 |
WO2005061599A1 (ja) * | 2003-12-24 | 2005-07-07 | Asahi Kasei Chemicals Corporation | ポリオレフィン製微多孔膜 |
JP2008081513A (ja) * | 2006-04-07 | 2008-04-10 | Tonen Chem Corp | ポリオレフィン微多孔膜及びその製造方法 |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH082983B2 (ja) * | 1988-05-12 | 1996-01-17 | 株式会社トクヤマ | 多孔性フィルムの製造方法 |
JPH05117440A (ja) * | 1991-10-31 | 1993-05-14 | Mitsubishi Kasei Corp | 多孔化ポリオレフインフイルムの製造方法 |
KR100667052B1 (ko) * | 1999-02-19 | 2007-01-10 | 토넨 케미칼 코퍼레이션 | 폴리올레핀 미세다공성 막과 그의 제조방법 |
JP3953840B2 (ja) * | 2002-02-28 | 2007-08-08 | 東燃化学株式会社 | ポリオレフィン微多孔膜の製造方法及びその製造方法によるポリオレフィン微多孔膜 |
JP4344550B2 (ja) * | 2002-06-25 | 2009-10-14 | 東燃化学株式会社 | ポリオレフィン微多孔膜の製造方法及びポリオレフィン微多孔膜 |
KR101050023B1 (ko) * | 2006-07-25 | 2011-07-19 | 아사히 가세이 케미칼즈 가부시키가이샤 | 폴리올레핀제 미다공막 권회물 및 그의 제조 방법 |
WO2008093572A1 (ja) * | 2007-01-30 | 2008-08-07 | Asahi Kasei E-Materials Corporation | ポリオレフィン製微多孔膜 |
JP5572334B2 (ja) | 2008-05-30 | 2014-08-13 | 旭化成イーマテリアルズ株式会社 | ポリオレフィン製微多孔膜 |
JP2011204587A (ja) * | 2010-03-26 | 2011-10-13 | Teijin Ltd | 非水系二次電池用セパレータ、非水系二次電池、および非水系二次電池用セパレータの製造方法 |
JP5630827B2 (ja) * | 2010-08-05 | 2014-11-26 | 日東電工株式会社 | ポリオレフィン多孔質膜およびその製造方法ならびにその製造装置 |
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Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000044709A (ja) * | 1998-07-27 | 2000-02-15 | Nitto Denko Corp | 多孔質フィルムの製造方法 |
WO2005061599A1 (ja) * | 2003-12-24 | 2005-07-07 | Asahi Kasei Chemicals Corporation | ポリオレフィン製微多孔膜 |
JP2008081513A (ja) * | 2006-04-07 | 2008-04-10 | Tonen Chem Corp | ポリオレフィン微多孔膜及びその製造方法 |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2017119769A (ja) * | 2015-12-28 | 2017-07-06 | 東レバッテリーセパレータフィルム株式会社 | ポリオレフィン微多孔膜とその製造方法、ロール及びポリオレフィン微多孔膜の評価方法 |
WO2018173904A1 (ja) * | 2017-03-22 | 2018-09-27 | 東レ株式会社 | ポリオレフィン微多孔膜、及びそれを用いた電池 |
JPWO2018173904A1 (ja) * | 2017-03-22 | 2020-01-23 | 東レ株式会社 | ポリオレフィン微多孔膜、及びそれを用いた電池 |
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